Diodes Offering Asymmetric Stability During Fluidic Assembly

ABSTRACT

Embodiments are related to systems and methods for fluidic assembly, and more particularly to systems and methods for assuring deposition of elements in relation to a substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.15/190,813 entitled “Diodes Offering Asymmetric Stability During FluidicAssembly” and filed Jun. 23, 2016 by Schuele et al. The entirety of theaforementioned application is incorporated herein by reference for allpurposes.

FIELD OF THE INVENTION

Embodiments are related to systems and methods for fluidic assembly, andmore particularly to systems and methods for assuring deposition ofelements in relation to a substrate.

BACKGROUND

LED displays, LED display components, and arrayed LED devices include alarge number of diodes formed or placed at defined locations across thesurface of the display or device. Forming or placing such a large numberof diodes often results in low throughput or in a number of defectswhich reduce the yield of a display or device manufacturing process.Some approaches to increasing throughput and yield include addingadditional diodes per pixel to provide enough redundancy to ensure thatat least a sufficient number of diodes per pixel are properly formed.This type of approach offers enhanced yield, but without adding a largenumber of redundant diodes per pixel, display yields are often stilllower than desired. Any yield less than one hundred percent within adisplay is costly both in an impact on profits and an impact onmanufacturing throughput.

Hence, for at least the aforementioned reasons, there exists a need inthe art for advanced systems and methods for manufacturing LED displays,LED display components, and LED devices.

SUMMARY

Embodiments are related to systems and methods for fluidic assembly, andmore particularly to systems and methods for assuring deposition ofelements in relation to a substrate.

This summary provides only a general outline of some embodiments of theinvention. The phrases “in one embodiment,” “according to oneembodiment,” “in various embodiments”, “in one or more embodiments”, “inparticular embodiments” and the like generally mean the particularfeature, structure, or characteristic following the phrase is includedin at least one embodiment of the present invention, and may be includedin more than one embodiment of the present invention. Importantly, suchphrases do not necessarily refer to the same embodiment. Many otherembodiments of the invention will become more fully apparent from thefollowing detailed description, the appended claims and the accompanyingdrawings.

BRIEF DESCRIPTION OF THE FIGURES

A further understanding of the various embodiments of the presentinvention may be realized by reference to the figures which aredescribed in remaining portions of the specification. In the figures,like reference numerals are used throughout several figures to refer tosimilar components. In some instances, a sub-label consisting of a lowercase letter is associated with a reference numeral to denote one ofmultiple similar components. When reference is made to a referencenumeral without specification to an existing sub-label, it is intendedto refer to all such multiple similar components.

FIG. 1 depicts a fluidic assembly system capable of moving a suspensioncomposed of a carrier liquid and a plurality of post enhanced diodesrelative to the surface of a substrate in accordance with one or moreembodiments of the present inventions;

FIGS. 2a-2e show a portion of a display including a substrate having anumber of wells each filled with a respective post enhanced diode inaccordance with embodiments of the present inventions;

FIGS. 3a-3d show a portion of a display including a well into which apost enhanced diode can be deposited in accordance with some embodimentsof the present inventions;

FIGS. 4a-4d show a portion of a display including a through hole viawell into which a post enhanced diode can be deposited in accordancewith other embodiments of the present inventions;

FIGS. 5a-5d show a portion of a display including a concentric groovedwell into which a post enhanced diode can be deposited in accordancewith one or more embodiments of the present inventions;

FIGS. 6a-6b are top views of alternate groove patterns in accordancewith other embodiments of the present inventions;

FIG. 7 is a flow diagram depicting a method for forming a post enhanceddiode in accordance with some embodiments of the present inventions; and

FIGS. 8-9 are flow diagrams showing methods for depositing or placingpost enhanced diodes into substrate wells in accordance with variousembodiments of the present inventions.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

Embodiments are related to systems and methods for fluidic assembly, andmore particularly to systems and methods for assuring deposition ofelements in relation to a substrate.

Various embodiments of the present inventions provide fluidic assemblysystems that include: a substrate and a suspension. The substrateincludes a plurality of wells, and the suspension includes a carrierliquid and a plurality of post enhanced diodes each including a postextending from a top surface of a diode structure. In some instances ofthe aforementioned embodiments, the systems further include a suspensionmovement device operable to move the suspension over the substrate suchthat a portion of the plurality of post enhanced diodes deposit inrespective ones of the plurality of wells.

In various instances of the aforementioned embodiments, the diodestructure of the post enhanced diodes includes: the top surface formedat least in part of a first electrically conductive material; a planarbottom surface formed at least in part of a second electricallyconductive material; a first electrical contact configured to conductcharge to the first electrically conductive material; and a secondelectrical contact configured to conduct charge to the secondelectrically conductive material. In one or more instances of theaforementioned embodiments, each of the plurality of wells includes athrough hole via extending through the substrate from the bottom of therespective well. In some such cases, a width of a surface of the postsubstantially parallel to the top surface of the diode structure isgreater than a width of the through hole via. In other such cases, thethrough hole via is off center from a substantially circular shapedbottom of the respective well.

In some instances of the aforementioned embodiments, a maximum width ofthe bottom surface is less than a maximum width of each of the pluralityof wells. In various instances of the aforementioned embodiments, anelectrical contact is formed on an interior surface of each of theplurality of wells. In some instances of the aforementioned embodiments,an orientation of each of the plurality of post enhanced diodes wherethe post extends away from the substrate is a non-inverted orientation,wherein an orientation of each of the plurality of post enhanced diodeswhere the post extends toward the substrate is an inverted orientation,and wherein one of the plurality of post enhanced diodes deposited in arespective well is more mechanically stable in the non-invertedorientation than in the inverted orientation. In one or more instancesof the aforementioned embodiments, an orientation of each of theplurality of post enhanced diodes where the post extends away from thesubstrate is a non-inverted orientation, an orientation of each of theplurality of post enhanced diodes where the post extends toward thesubstrate is an inverted orientation, and an orientation of one of theplurality of post enhanced diodes in contact with a surface of thesubstrate is more mechanically stable in the non-inverted orientationthan in the inverted orientation.

In various instances of the aforementioned embodiments, an orientationof each of the plurality of post enhanced diodes where the post extendsaway from the substrate is a non-inverted orientation, an orientation ofeach of the plurality of post enhanced diodes where the post extendstoward the substrate is an inverted orientation, and the substratefurther includes at least one groove configured such that an orientationof one of the plurality of post enhanced diodes traversing the groove ismore mechanically stable in the non-inverted orientation than in theinverted orientation. In some such instances, the groove extends intothe substrate with a leading edge exhibiting a slope greater than atrailing edge, and whereupon moving the suspension over the substrateone of the post enhanced diodes crosses the trailing edge beforecrossing the leading edge. In various such instances, a depth of thegroove into the substrate is less than a distance from an edge of thetop surface of the diode structure to an edge of the post. In one ormore such instances, a width of the groove at a surface of the substrateis less than a distance from an edge of the top surface of the diodestructure to an edge of the post.

Other embodiments of the present inventions provide post enhanceddiodes. Such post enhanced diodes include: a planar top surface formedat least in part of a first electrically conductive material; a planarbottom surface formed at least in part of a second electricallyconductive material; a post extending from the top surface; a firstelectrical contact configured to conduct charge to the firstelectrically conductive material; and a second electrical contactconfigured to conduct charge to the second electrically conductivematerial.

In some instances of the aforementioned embodiments, the top surfaceexhibits a first maximum width, a surface of the post that issubstantially parallel to the top surface exhibits a second maximumwidth, and the first maximum width is at least two times the secondmaximum width. In various instances of the aforementioned embodiments,the height of the post is measured from the top surface to the surfaceof the post that is substantially parallel to the top surface and thethickness of the diode structure is measured from the top surface andthe bottom surface. In some cases, the thickness-to-height ratio is in arange of 1:0.6 to 1:4. In one or more instances of the aforementionedembodiments, the top surface exhibits a maximum width and the thicknessof the diode structure is measured from the top surface and the bottomsurface. In some cases, the maximum width-to-thickness aspect ratio isin a range of 5:1 to 50:1.

In some instances of the aforementioned embodiments, the post is thefirst electrical contact. In various instances of the aforementionedembodiments, the post is formed of an insulator material. In some cases,the top surface is circular in shape, while in other instances the topsurface is polygonal in shape. In particular cases, the top surface ishexagonal in shape with a width of each facet of the hexagonsufficiently small to allow the top surface to fit within a given well.In various instances of the aforementioned embodiments, a surface of thepost that is substantially parallel to the top surface has a shapecircular in shape, while in other instances it is polygonal in shape. Inone or more instances of the aforementioned embodiments, the post isformed of a third conductive material which, in some cases, is the sameas the first conductive material. In some cases, the first conductivematerial is a p-doped semiconductor material, and the second conductivematerial is an n-doped semiconductor material. In some cases the postcan have a rounded top surface or surface with complex curvature, and inother cases it can have a substantially flat top surface. In othercases, multiple posts may exist on the diode top surface. The posts canbe center on the diode surface or they can be off-set.

Yet other embodiments provide substrates for fluidic assembly. Suchsubstrates include: a plurality of wells extending from a top surface ofthe substrate, where each of the plurality of wells is configured toaccept a post enhanced diode; and at least one groove extending into thetop surface of the substrate and configured such that an orientation ofthe post enhanced diodes traversing the groove is more mechanicallystable in a non-inverted orientation than in an inverted orientation.The post enhanced diode includes a post extending from a top surface ofa diode structure. When the post enhanced diode is in a non-invertedorientation, the post extends away from the top surface of thesubstrate. When the post enhanced diode is in an inverted orientation,the post extends toward the top surface of the substrate. In someinstances of the aforementioned embodiments, a depth of the groove intothe substrate is less than a distance from an edge of the top surface ofthe diode structure to an edge of the post. In various instances of theaforementioned embodiments, a width of the groove at a surface of thesubstrate is less than a distance from an edge of the top surface of thediode structure to an edge of the post.

Turning to FIG. 1, a fluidic assembly system 100 capable of moving asuspension 110 composed of a carrier liquid 115 and a plurality of postenhanced diodes 130 relative to the surface of a substrate 140 is shownin accordance with one or more embodiments of the present inventions. Insome embodiments, substrate 140 is formed of a polymer materiallaminated to the surface of a glass substrate. In particularembodiments, wells 142 are etched or otherwise formed in the laminatelayer. As used herein, the term “well” is used in its broadest sense tomean any surface feature into which a post enhanced diode may bedeposited. In other embodiments, the substrate is made of glass withwells 142 directly formed into the glass. Wells 142 may have flat andvertical surfaces as shown, or they may have bottoms and sides withcomplex curvatures. Based upon the disclosure provided herein, one ofordinary skill in the art will recognize a variety of materials,processes, and/or structures that may be used to form substrate 140. Forexample, substrate 140 can be formed of any material or compositioncompatible with fluidic device processing. This can include, but is notlimited to, glass, glass ceramic, ceramic, polymer, metal, or otherorganic or inorganic materials. As examples, wells 142 can be defined ina single material forming a surface feature layer when applied to thesurface of a base glass sheet. It is also possible for patternedconductor layers to exist between wells 142 formed in such a surfacefeature layer and the base glass layer. Substrate 140 can also be madeof multiple layers or combinations of these materials. Substrate 140 maybe a flat, curved, rigid, or flexible structure. In some cases,substrate 140 may end up being the final device substrate or it may onlyserve as an assembly substrate to position post enhanced diodes 130. Inthe case of an assembly substrate, post enhanced diodes 130 would thenbe transferred to the final device substrate in subsequent steps.

In some embodiments, carrier liquid 115 is isopropanol. Based upon thedisclosure provided herein, one of ordinary skill in the art willrecognize a variety of liquids, gasses, and/or liquid and gascombinations that may be used as the carrier liquid. It should be notedthat various analysis provided herein is based upon flow in a single,continuous direction or in other cases a relatively simple back-forthmotion, but that the flow may be more complex where both the directionand magnitude of fluid velocity can vary over time.

As shown in FIG. 1, post enhanced diodes 130 each include a relativelylarge diode structure and a smaller post extending from a top surface ofthe diode structure, and wells 142 in substrate 140 are each capable ofreceiving a given post enhanced diode 130 in a non-inverted orientation.As used herein, the phrase “post enhanced diode” is used broadly to meanany device with a post extending from a surface of either an anode orcathode of a diode structure such that at least a portion of an outeredge of the post is set back from an edge of the diode structure. Asused herein the phrase “non-inverted orientation” is used in itsbroadest sense to mean any orientation of a post enhanced diode 130 withthe post extending generally away from the top surface of substrate 140(i.e., away from the bottom of wells 142); and as used herein the phrase“inverted orientation” is used in its broadest sense to mean anyorientation of a post enhanced diode 130 with the post extendinggenerally toward the top surface of substrate 140 (i.e., toward from thebottom of wells 142). Using these definitions, post enhanced diodes 130a, 130 b, 130 f, and 130 g are each in a non-inverted orientation; andpost enhanced diodes 130 c, 130 d, and 130 e are each in an invertedorientation. The diode structure and post of post enhanced diodes 130are discussed in greater detail below in relation to FIGS. 2a-2e . Itshould be noted that in some cases the diode structure including ananode on one side and a cathode on the other can be referred to asasymmetric due to the different materials on each side of the diodestructure, however, the use of the term “asymmetric” in relation to adiode herein refers to any asymmetry of forces generated by liquidmovement around a post enhanced diode between an inverted orientationand a non-inverted orientation due to a post extending from the diodestructure. In some cases, the depth of wells 142 is substantially equalto the height of the diode structure of each of the post enhanced diodes130, and the inlet opening of wells 142 is greater that the width of thediode structure of each of the post enhanced diodes 130 such that onlyone post enhanced diode 130 deposits into any given well 142. It shouldbe noted that while embodiments discuss post enhanced diodes thatinclude a single post extending from a diode structure, that variousembodiments provide post enhanced diodes that each include two or moreposts each extending from the same diode structure.

A depositing device 150 deposits suspension 110 over the surface ofsubstrate 140 with suspension 110 held on top of substrate 140 by sides120 of a dam structure. In some embodiments, depositing device 150 is apump with access to a reservoir of suspension 110. A suspension movementdevice 160 agitates suspension 110 deposited on substrate 140 such thatpost enhanced diodes 130 move relative to the surface of substrate 140.As post enhanced diodes 130 move relative to the surface of substrate140 they deposit into wells 142 in either a non-inverted orientation oran inverted orientation. In some embodiments, suspension movement device160 is a brush that moves in three dimensions. Based upon the disclosureprovided herein, one of ordinary skill in the art will recognize avariety of devices that may be used to perform the function ofsuspension movement device 160 including, but not limited to, a pump.

When deposited in the inverted orientation (e.g., post enhanced diode130 d), the movement generated by suspension movement device 160generates force likely to dislocate an inverted post enhanced diode 130from a given well 142. In contrast, when deposited in the non-invertedorientation (e.g., post enhanced diode 130 g), the force on thedeposited, non-inverted post enhanced diode 130 caused by suspensionmovement device 160 is unlikely to dislocate the post enhanced diodefrom a given well 142. In some embodiments, the likelihood ofdislocating an inverted post enhanced diode 130 from a well 142 is muchgreater than the likelihood of dislocating a non-inverted post enhanceddiode 130 from a well 142. In some embodiments the moment of forcerequired to dislocate an inverted post enhanced diode 130 from a well142 is between 0.01×10⁻¹⁴N-m and 1.0×10⁻¹⁴N-m depending upon the widthto height ratio of the post and the diameter of the diode structure(where a positive value of the moment of force indicates the diodestructure of a post enhanced diode 130 is being forced to rotate about apoint of rotation); and the moment of force required to dislocate anon-inverted post enhanced diode 130 from a well 142 is a negative value(where a negative value of the moment of force indicates the diodestructure of a post enhanced diode 130 is being pushed down on thesurface of substrate 140) for the same width to height ratio of the postand thickness of the diode structure making any displacement unlikely.As used herein, a post enhanced diode is considered “likely todislocate” where the moment of force is a positive value, and isconsidered “unlikely to dislocate” where the moment of force is anegative value.

Similarly, when moving across the surface of substrate 140 in theinverted orientation (e.g., post enhanced diode 130 e), the movementgenerated by suspension movement device 160 generates a force likely toflip an inverted post enhanced diode 130. In contrast, when movingacross the surface of substrate 140 in the non-inverted orientation(e.g., post enhanced diode 130 f), the force on the non-inverted postenhanced diode 130 caused by suspension movement device 160 is lesslikely to flip the post enhanced diode. In some embodiments, thelikelihood of flipping an inverted post enhanced diode 130 moving nearthe surface of substrate 140 is greater than the likelihood of flippinga non-inverted post enhanced diode 130 moving similarly near the surfaceof substrate 140 as the moment of force for the inverted post enhanceddiode 130 is greater than the moment of force for the non-inverted postenhanced diode 130.

A capture device 170 includes an inlet extending into suspension 110 andcapable of recovering a portion of suspension 110 including a portion ofcarrier liquid 115 and non-deposited post enhanced diodes 130, andreturning the recovered material for reuse. In some embodiments, capturedevice 170 is a pump. More detail regarding the interaction of postenhanced diodes 130 with substrate 140 and wells 142 is provided inrelation to FIGS. 3-5 below.

Turning to FIG. 2a , a top view 200 of a substrate portion 230 is shownincluding a number of wells 205 into which post enhanced diodes 210 havebeen successfully deposited. Each of post enhanced diodes 210 of FIG. 2aare represented in a top view 235 of FIG. 2b , a cross sectional view250 of FIG. 2c , and a circuit symbol 280 of a post enhanced diode 210operating as an LED. Post enhanced diodes 210 include one or morefeatures that enable the relative flow of a carrier liquid about postenhanced diodes 210 to create a net moment of force for increasing alikelihood of flipping post enhanced diodes 210 from a first orientationto a second orientation, with a dissimilar (i.e., asymmetric) likelihoodof flipping post enhanced diodes 210 from the second orientation to thefirst orientation. These features may include sidewall angles, surfacestructures such as posts, or the general shape of the post enhanceddiodes 210. Notably, the aforementioned structures and shapes of thepost enhanced diodes 210 that encourage asymmetric re-orientation may ormay not be present in a final display incorporating post enhanced diodes210.

As shown in FIGS. 2b-2c , post enhanced diode 210 includes a planar topsurface 245 of an electrically conductive material 260 (shown as anun-patterned region). As used herein, the term “planar” is used in itsbroadest sense to mean two dimensional with exception of defects orprocess related variance standard in semiconductor manufacturingprocesses. In some embodiments, electrically conductive material 260 isp-doped Gallium Nitride (GaN). A post 255 (show as a hatched patternregion) extending from top surface 245 is also shown. A top surface 240of post 255 is also shown. In some embodiments, post 255 is formed ofelectrically conductive material 260 (i.e., a homogeneous post). Inother embodiments, post 255 is formed of a material other thanelectrically conductive material 260 (i.e., a heterogeneous post). Insome cases, a heterogeneous post is formed at least in part of aninsulating layer such as SiO₂, and in other cases a heterogeneous postis formed of a conductive material such as a metal compatible withdeposition on electrically conductive material 260. It should be notedthat while post 255 is shown as substantially centered on top surface245, in other embodiments post 255 may be offset from a center positionat any location from a center point of top surface 245 to a radialdistance from the center point such that a portion, but not all of theedges, of post 255 is coextensive with an edge of a diode structure 285.In some cases the post can have a rounded top surface or surface withcomplex curvature, and in other cases it can have a substantially flattop surface. In other cases, multiple posts may exist on the diode topsurface.

Various approaches may be used for forming post 255 on diode structure285. For example, fabricating a homogeneous post may include etching thetop surface of a thick layer of electrically conductive material 260 toyield the combination of both post 255 and the layer of electricallyconductive material 260 shown in cross sectional view 250; or by formingthe layer of electrically conductive material 260 followed by selectiveepitaxial growth using the same material to form post 255. As otherexamples, fabricating a heterogeneous post may include etching the postfrom a film that is deposited onto top surface 245 of diode structure285, or by forming a post with a different material through plating or atemplated growth process on top of top surface 245 of diode structure285. This latter approach permits the use of any material for the post(e.g., dielectrics, metals, etc.). In some cases, photolithography of aphoto resist may be used in relation to the aforementioned plating ortemplate growth.

Top surface 245 includes one or more electrical contacts 282, 286 thatconduct charge from a signal source (not shown) to electricallyconductive material 260. In some embodiments, electrical contacts 282,286 are formed of a metal deposited onto the layer of electricallyconductive material 260. In other embodiments, electrical contacts 282,286 are an exposed area of top surface 245 to which a signal source (notshown) can contact electrically conductive material 260. In someembodiments where post 255 is formed of a conductive material itoperates as a post. In one particular embodiment where post 255 isformed of electrically conductive material 260, an exposed area of topsurface 240 to which a signal source (not shown) can contactelectrically conductive material 260 operates as an electrical contact.

The layer of electrically conductive material 260 is disposed on top ofa multiple quantum well (MQW) 265 (shown as a hatched pattern region),which in turn is disposed on top of a layer of an electricallyconductive material 270 (shown as an un-patterned region). In someembodiments, electrically conductive material 270 is n-doped GalliumNitride (GaN). MQW 265 may be formed of any material compatible withboth electrically conductive material 260 and electrically conductivematerial 270, and which when sandwiched between electrically conductivematerial 260 and electrically conductive material 270 is capable ofoperating as a light emitting diode (LED). Together, the layer ofelectrically conductive material 260, MQW 265, and the layer ofelectrically conductive material 270 form a diode structure of postenhanced diodes 210. Based upon the disclosure provided herein, one ofordinary skill in the art will recognize a variety of materials andmaterial combinations that may be used in forming diode structure 285 ofa given post enhanced diode 210. As different post enhanced diodes 210are intended to emit light of different wavelengths (e.g., red, green,blue), the construction and/or materials for different instances of postenhanced diodes 210 will vary to achieve a desired color distribution.

The layer of electrically conductive material 270 includes a planarbottom surface 275. Bottom surface 275 includes one or more electricalcontacts 284, 288 that conduct charge from a signal source (not shown)to electrically conductive material 270. In some embodiments, electricalcontacts 284, 284 are formed of a metal deposited onto the layer ofelectrically conductive material 270. In other embodiments, electricalcontacts 284, 288 are an exposed area of bottom surface 275 to which asignal source (not shown) can contact electrically conductive material270. In particular cases, electrical contacts 284, 288 are two sides ofthe same contact extending as a concentric circle of exposedelectrically conductive material 270 around the perimeter of bottomsurface 275.

Post 255 has a width (Wp) and a height (Hp), and diode structure 285 hasa width (Wd) and a height (Hd). As more fully discussed below inrelation to FIG. 2e , the sides of post 255 and diode structure 285 insome cases are not perfectly vertical and may vary. In such a case, theaforementioned width and height characteristics of post 255 and diodestructure 285 are considered to be: the maximum width where the widthvaries as a function of height, and the maximum height where the heightvaries as a function of width. In some embodiments, the width:heightratio of diode structure 285 (i.e., Wd:Hd) is between 5:1 and 50:1. Insome particular embodiments, the width:height ratio of diode structure285 (i.e., Wd:Hd) is between 5:1 and 30:1. In some embodiments, thewidth:height ratio of post 255 (i.e., Wp:Hp) is between 2:1 and 5:1. Invarious embodiments, the height of diode structure 285 (i.e., Hd) isbetween 4 μm and 7 μm, and the height of post 255 (i.e., Hp) is between2 μm and 7 μm, in part depending upon the desired ratio of Hd to Hp.

The dimensions of post 255 can affect the stability of an inverted postenhanced diode 210. In particular, if the post is too small, postenhanced diode 210 will not be as likely to flip into a non-invertedorientation. Numerical modeling of the fluidic process shows that, for a50-m-diameter (Wd) diode structure that is 5 μm thick (Hd) exposed to aflow velocity of a carrier liquid of 4.6 mm/s, a post with dimensions of10 μm×5 μm (Wp×Hp) will flip the disk to the non-inverted orientation.Models with varying post dimensions on a 50-μm-diameter (Wd) disk diodestructure that are captured in a 3 μm deep well have shown that smallposts (e.g., with a height (Hp) less than or equal to 4 μm) exposed to asimilar flow velocity as above, have little influence on theorientation, but a 5-μm high (Hp) post is sufficient to cause aninverted post enhanced diode 210 to flip while a non-inverted postenhanced diode 210 will remain in a non-inverted orientation.Experimental data has demonstrated that the modeling revealing theaforementioned dimensions is reliable, and that a post with dimensionsof 12 μm×3 μm (Wp×Hp) is able to influence the orientation offluidically-aligned disks, with a yield of over 99.7% of disks (out of150 disks) having a desired non-inverted orientation. The followingtable shows additional modeling data for the net moment of force forinverted post enhanced diodes 210 having different diode structurewidths (Wd) and ratios of post height to width (Hp×Wp):

Wp × Hp = 10 × 5 Wp × Hp = 15 × 5 Wp × Hp = 20 × 5 Wp × Hp = 20 × 7 Wd =40 μm +0.29 × 10⁻¹⁴ N-m — — — Wd = 50 μm +0.52 × 10⁻¹⁴ N-m — — — Wd = 70μm −0.29 × 10⁻¹⁴ N-m −0.11 × 10⁻¹⁴ N-m +0.07 × 10⁻¹⁴ N-m — Wd = 90 μm−1.57 × 10⁻¹⁴ N-m −1.33 × 10⁻¹⁴ N-m −1.13 × 10⁻¹⁴ N-m +0.09 × 10⁻¹⁴ N-m

Turning to FIG. 2e , a cross sectional view 290 of another embodiment ofa post enhanced diode 210 where side walls 291, 292 of post 255 andsidewalls 295, 296 of diode structure 285 each exhibit a tapered slopecompared with the vertical slope shown in cross sectional view 250 ofFIG. 2c . As discussed above, where the sidewalls are tapered (i.e.,vary as a function of height), the width of the post (Wp) is the maximumwidth thereof, and the width of diode structure 285 (Wd) is the maximumwidth thereof as shown in cross sectional view 290. The taper exhibitedby the sidewalls will vary dependent upon the processes and materialsused for constructing post enhanced diodes 130 as is known in the art.Similar tapering may occur on the sides of wells 205. It should be notedthat addition of the post to diode structure 285 results an asymmetry offorces generated by liquid movement around a plate diode between aninverted orientation and a non-inverted orientation. As such, the postneed not be a perfectly vertical structure, but rather may be anystructure sufficient to result in a net positive moment of force whenpost enhanced diode 210 is in an inverted orientation, and asubstantially lower moment of force when post enhanced diode 210 is in anon-inverted orientation such that post enhanced diodes 210 will prefera non-inverted orientation. In some cases, the depth of wells 205 issubstantially equal to the height of diode structure 285 of each of thepost enhanced diodes 210, and the inlet opening of wells 205 is greaterthat the width of diode structure 285 of each of the post enhanceddiodes 210 such that only one post enhanced diode 210 deposits into anygiven well 205.

Once post enhanced diodes 210 are deposited in wells 205 with post 255extending away from substrate portion 230, one or more electricalcontacts in wells 205 are connected to one or more electrical contactson bottom surface 275 of post enhanced diodes 210, and one or moreprocessing steps are performed to electrically connect one or moreelectrical contacts on top surface 245 of post enhanced diodes 210 tocontrollable signals. Upon completion of such processing, post enhanceddiodes 210 can be individually controlled causing a display includingsubstrate portion 230 and post enhanced diodes 210 to display a desiredimage. Post enhanced diodes 210 as discussed herein may be used, amongother things, to fabricate both direct emission displays andlocally-addressed backlight units.

Turning to FIGS. 3a-3b , a top view 300 and a cross sectional view 301of a portion of a display including a well 312 into which a postenhanced diode 210 can be deposited is depicted in accordance with someembodiments of the present inventions. As shown, the display includes asubstrate 390 composed of a polymer material 315 laminated to thesurface of a glass substrate 305. It should be noted that materialsother than glass may be used in place of glass substrate. Additionally,other conductive or non-conductive layers may exist between materials315 and 305. Further, it should be noted that in some cases polymermaterial 315 may be replaced by glass or another suitable material. Insome embodiments, substrate 315 is made by forming an electric contactlayer on the surface of glass substrate 305, and etching the electriccontact layer to yield an electrical contact 335 at a locationcorresponding to a future well. It should be noted that while electricalcontact 335 is shown as a donut shape, that it may be a solid circleshape as there is not a through hole via or another suitable shape forforming an electrical contact in the bottom of a well. Polymer material315 is then laminated over glass substrate 305 and electrical contact335, followed by an etch of polymer material 315 to open well 312defined by a sidewall 314 and expose a portion of electrical contact335. Electrical contact 335 may be formed of any material capable offorming an electrical junction with bottom surface 275 of a postenhanced diode 210. In some cases, electrical contact 335 is formed of ametal that when annealed with a post enhanced diode 210 disposed withinwell 312 forms an electrically conductive location between a signalconnected to electrical contact 335 and electrically conductive material270 of a post enhanced diode 210. In some embodiments, the depth of well312 is substantially equal to the height of the diode portion (Hd) of apost enhanced diode 210 such that only one post enhanced diode 210deposits in well 312.

During fluidic assembly a liquid flow (indicated by arrows 360) resultsin drag forces on post enhanced diodes 210 traversing the surface ofsubstrate 390. Because post enhanced diodes 210 include a post 255extending from the diode structure, the drag forces have an asymmetricimpact on the orientation of the plate diodes. In particular, the dragforces result in a positive moment of force about a fixed point ofrotation (e.g., an edge of the diode structure in contact with thesurface of substrate 390) that will flip an inverted post enhanced diode210 into a non-inverted orientation. In contrast, the drag forces on anon-inverted post enhanced diode 210 due to the liquid flow areprimarily due to perturbations around post 255, and the forces exertedon the diode structure of a post enhanced diode 210 lead to a negativenet moment of force. This negative net moment of force the leading edge(i.e., the edge leading in the direction of arrows 360) of the diodestructure down and stabilizes the post enhanced diode 210 in thenon-inverted orientation.

A similar asymmetric impact of the drag forces occurs between a postenhanced diode 210 deposited in a non-inverted orientation in well 312(shown in a cross sectional view 302 of FIG. 3c ), and a post enhanceddiode 210 deposited in an inverted orientation in well 312 (shown in across sectional view 303 of FIG. 3d ). As shown in FIG. 3c , any momentof force around the lower right corner of post enhanced diode 210 causedby the liquid flow is offset by forces exerted on top surface 245 ofpost enhanced diode 210 resulting in a negative net moment of forcetending to maintain post enhanced diode 210 deposited in well 210. Asshown in FIG. 3d , when post enhanced diode 210 is inverted in well 312top surface 245 acts a hydrofoil generating a lifting force from theliquid flow such that a net positive moment of force results around theright side of post enhanced diode 210 contacting side 314 of well 312.This net positive moment of force tends to cause post enhanced diode 210to flip in a direction indicated by an arrow 370 such that post enhanceddiode 210 is forced out of well 312 and possibly into a non-invertedorientation as the liquid flow moves post enhanced diode 210 towardanother downstream well where it may re-deposit.

Turning to FIGS. 4a-4b , a top view 400 and a cross sectional view 401of a portion of a display including a through hole via well 412 intowhich a post enhanced diode 210 can be deposited is depicted inaccordance with some embodiments of the present inventions. As shown,the display includes a substrate 490 composed of a polymer material 415laminated to the surface of a glass substrate 405. Additionally, otherconductive or non-conductive layers may exist between materials 415 and405. It should be noted that materials other than glass may be used inplace of glass substrate. Further, it should be noted that in some casespolymer material 415 may be replaced by glass or another suitablematerial. In some embodiments, substrate 415 is made by forming anelectric contact layer on the surface of glass substrate 405, andetching the electric contact layer to yield an electrical contact 435 ata location corresponding to a future well. Polymer material 415 is thenlaminated over glass substrate 405 and electrical contact 435, followedby an etch of polymer material 415 to open well 412 and expose a portionof electrical contact 435. Electrical contact 435 may be formed of anymaterial capable of forming an electrical junction with bottom surface275 of a post enhanced diode 210. In some cases, electrical contact 435is formed of a metal that when annealed with a post enhanced diode 210disposed within well 412 forms an electrically conductive locationbetween a signal connected to electrical contact 435 and electricallyconductive material 270 of a post enhanced diode 210. In someembodiments, the depth of well 412 is substantially equal to the heightof the diode portion (Hd) of a post enhanced diode 210 such that onlyone post enhanced diode 210 deposits in well 412.

An additional process is performed to form a through hole via 425extending through glass substrate 405. In some cases, the width ofthrough hole via 425 (Wv) is less than a minimum width of post 255 toassure that post 255 does not insert into through hole via 425 when postenhanced diode 210 is inverted in well 412 as such insertion would limitthe ability for post enhanced diode 210 to flip out of well 412. Inother cases, through hole via 425 is substantially centered in well 512and post 255 is considerably off-center on top surface 425 of the diodestructure, or through hole via 425 is considerably off-center in thebase of well 512 and post 255 is substantially centered on top surface425 of the diode structure such that when a post enhanced diode 210deposits in well 512 in an inverted orientation post 255 does not alignwith through hole via 425.

During fluidic assembly a liquid flow (indicated by arrows 460) resultsin drag forces on post enhanced diodes 210 traversing the surface ofsubstrate 490. Because post enhanced diodes 210 include a post 255extending from the diode structure, the drag forces have an asymmetricimpact on the orientation of the plate diodes. In particular, the dragforces result in a positive moment of force about a fixed point ofrotation (e.g., an edge of the diode structure in contact with thesurface of substrate 490) that will flip an inverted post enhanced diode210 into a non-inverted orientation. In contrast, the drag forces on anon-inverted post enhanced diode 210 due to the liquid flow areprimarily due to perturbations around post 255, and the forces exertedon the diode structure of a post enhanced diode 210 lead to a negativenet moment of force. This negative net moment of force the leading edge(i.e., the edge leading in the direction of arrows 460) of the diodestructure down and stabilizes the post enhanced diode 210 in thenon-inverted orientation.

A similar asymmetric impact of the drag forces occurs between a postenhanced diode 210 deposited in a non-inverted orientation in well 412(shown in a cross sectional view 402 of FIG. 4c ), and a post enhanceddiode 210 deposited in an inverted orientation in well 412 (shown in across sectional view 403 of FIG. 4d ). As shown in FIG. 4c , any momentof force around the lower right corner of post enhanced diode 210 causedby the liquid flow is offset by forces exerted on top surface 245 ofpost enhanced diode 210 resulting in a negative net moment of forcetending to maintain post enhanced diode 210 deposited in well 210. Asshown in FIG. 4d , when post enhanced diode 210 is inverted in well 412top surface 245 acts a hydrofoil generating a lifting force from theliquid flow such that a net positive moment of force results around theright side of post enhanced diode 210 contacting a side of well 412.This net positive moment of force tends to cause post enhanced diode 210to flip in a direction indicated by an arrow 470 such that post enhanceddiode 210 is forced out of well 412 and possibly into a non-invertedorientation as the liquid flow moves post enhanced diode 210 towardanother downstream well where it may re-deposit.

Additionally, a suction may be applied to the bottom side of substrate490. When post enhanced diode 210 deposits in well 412 in a non-invertedorientation such as that shown in cross sectional view 402, the appliedsuction force further stabilizes post enhanced diode 210 in well 412. Itshould be noted that the applied suction also provides somestabilization of a post enhanced diode 210 deposited in well 412 in aninverted orientation, but the stabilization due to the suction on anon-inverted post enhanced diode 210 is substantially greater than thaton an inverted post enhanced diode 210. Such suction allows forincreased assembly speed. Additionally, at the end of fluidic assemblyafter depositing or placing post enhanced diodes in a number of wells, aclean up process is performed to remove any excess post enhanced diodes.The addition of the suction force allows for a more aggressive clean upoperation including, for example, flowing a cleaning fluid over thesurface of substrate 490 at a much higher rate than that used during thedeposition process without disturbing the deposited post enhanced diodes210 held in place in part by the added suction force.

Turning to FIGS. 5a-5b , a top view 500 and a cross sectional view 501of a portion of a display including a through hole via well 512 intowhich a post enhanced diode 210 can be deposited is depicted inaccordance with some embodiments of the present inventions. As shown,the display includes a substrate 590 composed of a polymer material 515laminated to the surface of a glass substrate 505. It should be notedthat materials other than glass may be used in place of glass substrate.Additionally, other conductive or non-conductive layers may existbetween materials 515 and 505. Further, it should be noted that in somecases polymer material 515 may be replaced by glass or another suitablematerial. In some embodiments, substrate 515 is made by forming anelectric contact layer on the surface of glass substrate 505, andetching the electric contact layer to yield an electrical contact 535 ata location corresponding to a future well. Polymer material 515 is thenlaminated over glass substrate 505 and electrical contact 535, followedby an etch of polymer material 515 to open well 512 and expose a portionof electrical contact 535. Electrical contact 535 may be formed of anymaterial capable of forming an electrical junction with bottom surface275 of a post enhanced diode 210. In some cases, electrical contact 535is formed of a metal that when annealed with a post enhanced diode 210disposed within well 512 forms an electrically conductive locationbetween a signal connected to electrical contact 535 and electricallyconductive material 270 of a post enhanced diode 210. In someembodiments, the depth of well 512 is substantially equal to the heightof the diode portion (Hd) of a post enhanced diode 210 such that onlyone post enhanced diode 210 deposits in well 512.

An additional process is performed to form a through hole via 525extending through glass substrate 505. In some cases, the width ofthrough hole via 525 (Wv) is less than a minimum width of post 255 toassure that post 255 does not insert into through hole via 525 when postenhanced diode 210 is inverted in well 512 as such insertion would limitthe ability for post enhanced diode 210 to flip out of well 512. Inother cases, through hole via 525 is substantially centered in well 512and post 255 is considerably off-center on top surface 525 of the diodestructure, or through hole via 525 is considerably off-center in thebase of well 512 and post 255 is substantially centered on top surface525 of the diode structure such that when a post enhanced diode 210deposits in well 512 in an inverted orientation post 255 does not alignwith through hole via 525.

Further, substrate 590 is etched to form a groove 510 concentricallyaround well 512. As shown, in some embodiments groove 510 exhibits onesubstantially vertical side wall and one highly tapered side wall. Thetapered side wall is less likely to catch a leading edge of postenhanced diode 210 traversing the surface of substrate 590 in either anon-inverted orientation (shown in a cross sectional view 502 of FIG. 5c) or an inverted orientation (shown in a cross sectional view 503 ofFIG. 5c ) in a direction indicated by an arrow 570. As the edge catches,a moment of force develops around the edge inducing post enhanced diode210 to flip. In contrast, a more vertical side wall on groove 510 ismore likely to catch a leading edge of post enhanced diode 210traversing the surface of substrate 590 in an inverted orientation(shown in cross sectional view 503 of FIG. 5c ), but unlikely to catchthe leading edge of post enhanced diode 210 traversing in a non-invertedorientation (shown in cross sectional view 502 of FIG. 5c ). To limitthe ability for groove 510 to catch the leading edge of post enhanceddiode 210 traversing in a non-inverted orientation (shown in crosssectional view 502 of FIG. 5c ), the width of groove 510 is relativelysmall. In some embodiments, the width of groove is less than twenty-fivepercent of the width of the diode structure (Wd). Groove 510 should bedesigned such that it is large enough to catch a leading edge of aninverted post enhanced diode 210, but small enough to let a non-invertedpost enhanced diode 210 pass without catching a leading edge. As furtherguidance to avoiding catching a leading edge of a non-inverted postenhanced diode 210, groove 510 should be flush with the surface ofsubstrate 590.

It should be noted that other shapes for groove 510 are possible inaccordance with other embodiments of the present invention. For example,groove 510 may include two substantially vertical walls with each wallabout equal in catching a leading edge of a post enhanced diode 210traversing the surface of substrate 590 in an inverted orientation.Thus, regardless of the direction that a post enhanced diode 210 istraversing the surface of substrate 590, it is equally likely to catchand flip. In such cases, it may be desirable to make the width of groove510 less than the width of post 255 to avoid the possibility of post 255inserting into groove 510 and becoming trapped.

During fluidic assembly a liquid flow (indicated by arrows 560) resultsin drag forces on post enhanced diodes 210 traversing the surface ofsubstrate 590. Because post enhanced diodes 210 include a post 255extending from the diode structure, the drag forces have an asymmetricimpact on the orientation of the plate diodes. In particular, the dragforces result in a positive moment of force about a fixed point ofrotation (e.g., an edge of the diode structure in contact with thesurface of substrate 590) that will flip an inverted post enhanced diode210 into a non-inverted orientation. In contrast, the drag forces on anon-inverted post enhanced diode 210 due to the liquid flow areprimarily due to perturbations around post 255, and the forces exertedon the diode structure of a post enhanced diode 210 lead to a negativenet moment of force. This negative net moment of force about the leadingedge (i.e., the edge leading in the direction of arrows 560) of thediode structure holds the diode structure down and stabilizes the postenhanced diode 210 in the non-inverted orientation.

In some cases, the drag forces on an inverted post enhanced diode 210traversing the surface of substrate 590 are insufficient to cause achange in orientation. This may be in part due to the difference betweenthe rate at which the carrier fluid is flowing and the rate at which theinverted post enhanced diode 210 is moving is insufficient. However,when a leading edge of an inverted post enhanced diode 210 catches ingroove 510, the relative rate at which the carrier fluid is flowing andthe rate at which the inverted post enhanced diode 210 is movingincreases. This increase in the relative velocity results in acorresponding increase in drag forces and likelihood of flipping. Asgroove 510 is less likely to catch a leading edge of a non-inverted postenhanced diode 210, the impact of the groove on non-inverted postenhanced diodes 210 is insubstantial.

While the preceding embodiment disclosed a groove concentric around awell, other locations and geometries for a groove may be used inaccordance with different embodiments. For example, FIG. 6a shows a topview 600 of a substrate portion 605 including a number of wells 610 intowhich post enhanced diodes 210 may be deposited. In addition, a numberof parallel grooves 620 are formed in the surface of substrate portion605 such that the direction of flow (shown by an arrow 601) is generallyperpendicular to grooves 620. In this configuration, grooves 620 perturbthe orientation of inverted post enhanced diodes 210 traversingsubstrate portion 605 similar to that discussed above in relation toFIG. 5. As another example, FIG. 6b shows a top view 650 of a substrateportion 655 including a number of wells 660 into which post enhanceddiodes 210 may be deposited. In addition, a number of parallel grooves670 are formed in the surface of substrate portion 655 such that thedirection of flow (shown by an arrow 651) is generally perpendicular togrooves 670. In this configuration, grooves 670 perturb the orientationof inverted post enhanced diodes 210 traversing substrate portion 655similar to that discussed above in relation to FIG. 5.

Turning to FIG. 7, a flow diagram 700 depicts a method for forming apost enhanced diode in accordance with some embodiments of the presentinventions. Following flow diagram 700, a first doped layer is formed(block 705). The first doped layer is formed by doping a semiconductormaterial with a first dopant type which is either a p-type dopant or ann-type dopant. Any process known in the art for forming a doped materialmay be used. In some embodiments, the first doped layer is an n-dopedGaN layer.

An MQW layer is formed on the first doped layer (block 710). Any processknown in the art for forming an MQW layer may be used. A second dopedlayer is formed on top of the MQW layer (block 715). The second dopedlayer is formed by doping a semiconductor material with a second dopanttype which is the opposite doping of the first dopant type. Any processknown in the art for forming a doped material may be used. In someembodiments where the first doped layer is an n-doped GaN layer, thesecond doped layer is a p-doped GaN layer.

A post is formed on the second doped layer (block 720). Variousapproaches may be used for forming a post extending from the seconddoped layer. For example, fabricating a homogeneous post may be done aspart of the second doped layer where a semiconductor material is formedon the MQW layer, and then etched back leaving a thick post structureand a thinner layer of the semiconductor extending from the edges of thepost to the edges of the MQW layer. In this case, the second doped layermay be doped after the post is formed. As another example, the post maybe formed on the second doped layer after the second doped layer hasbeen doped through selective epitaxial growth using the same material toas the second doped layer. As other examples, forming a heterogeneouspost may include etching the post from a film that is deposited onto thesecond doped layer, or by forming a post with a different materialthrough plating or a templated growth process on top the second dopedlayer. This latter approach permits the use of any material for the post(e.g., dielectrics, metals, etc.). In some cases, photolithography of aphoto resist may be used in relation to the aforementioned plating ortemplate growth. While not shown in flow diagram 700, individual postenhanced diodes can then be cut by etching through the combination ofthe second doped material, the MQW layer, and the first doped materialto yield individual post enhanced diodes similar to those discussedabove in relation to FIGS. 2b -2 e.

Turning to FIG. 8, a flow diagram 800 shows a method for depositing orplacing post enhanced diodes into substrate wells in accordance withvarious embodiments of the present inventions. Following flow diagram800, a substrate is formed including a plurality of wells each capableof accepting a post enhanced diode (block 810). The substrate may beformed similar to that discussed above in relation to any of FIGS. 3-5.In addition, a suspension is formed by adding a plurality of postenhanced diodes to a carrier liquid (block 805). In some cases, thecarrier liquid is isopropanol, but may be another liquid or gas capableof moving post enhanced diodes across the surface of a substrate.

The suspension is deposited on a surface of the substrate that includesthe wells (block 815). This deposit may be done by any suitable methodincluding, but not limited to, pumping the suspension or draining thesuspension onto the surface. The suspension is then agitated on thesubstrate such that the plurality of post enhanced diodes in thesuspension move relative to the surface of the substrate and depositinto respective ones of the plurality of wells (block 820). Because ofthe asymmetry of force due to the post extending from a top surface of adiode structure, the post enhanced diodes tend to assume a non-invertedorientation when exposed to movement of the carrier liquid. Thesuspension including non-deposited post enhanced diodes and the carrierliquid is removed from the surface of the substrate in a clean-upprocess (block 825).

Turning to FIG. 9, a flow diagram 900 shows another method fordepositing or placing post enhanced diodes into substrate wells inaccordance with various embodiments of the present inventions. Followingflow diagram 900, a substrate is formed including a plurality of wellseach capable of accepting a post enhanced diode and at least one groovecapable of catching a leading edge of an inverted post enhanced diodetraversing the surface of the substrate (block 810). The substrate maybe formed similar to that discussed above in relation to any of FIGS.3-5, and include a groove pattern similar to that discussed above inrelation to FIGS. 5-6. In addition, a suspension is formed by adding aplurality of post enhanced diodes to a carrier liquid (block 805). Insome cases, the carrier liquid is isopropanol, but may be another liquidor gas capable of moving post enhanced diodes across the surface of asubstrate.

The suspension is deposited on a surface of the substrate that includesthe wells (block 915). This deposit may be done by any suitable methodincluding, but not limited to, pumping the suspension or draining thesuspension onto the surface. The suspension is then agitated on thesubstrate such that the plurality of post enhanced diodes in thesuspension move relative to the surface of the substrate and depositinto respective ones of the plurality of wells (block 920). Because ofthe asymmetry of force due to the post extending from a top surface of adiode structure, the post enhanced diodes tend to assume a non-invertedorientation when exposed to movement of the carrier liquid. Further,because of the possibility of inverted post enhanced diodes catching aleading edge in the groove on the surface of the substrate as they moveacross the substrate, the tendency of the post enhanced diodes to assumea non-inverted orientation when exposed to movement of the carrierliquid is increased. The suspension including non-deposited postenhanced diodes and the carrier liquid is removed from the surface ofthe substrate in a clean-up process (block 925).

One of ordinary skill in the art will recognize various advantagesachievable through use of different embodiments of the inventions. Asjust some of many advantages, lower display costs are possible as asignificant cost of manufacturing a microLED display is the materialcost of the microLEDs themselves. As some embodiments of the presentinventions allow for reducing redundancy otherwise necessary to assurean operable display, the overall number of microLEDs may be reducedresulting in a corresponding reduction in costs. Various embodiments ofthe present inventions do not require lock-n-key type interactionbetween post enhanced diodes and wells which allow diodes to deposit inonly a single orientation. As such, manufacturing tolerances may bereduced leading to greater yields and/or lower costs. Based upon thedisclosure provided herein, one of ordinary skill in the art willrecognize a variety of other advantages achievable through use of one ormore embodiments of the present inventions.

In conclusion, the invention provides novel systems, devices, methodsand arrangements for fluidic assembly. While detailed descriptions ofone or more embodiments of the invention have been given above, variousalternatives, modifications, and equivalents will be apparent to thoseskilled in the art without varying from the spirit of the invention. Forexamples, while some embodiments are discussed in relation to displays,it is noted that the embodiments find applicability to devices otherthan displays. Therefore, the above description should not be taken aslimiting the scope of the invention, which is defined by the appendedclaims.

What is claimed is:
 1. A substrate for fluidic assembly, the substratecomprising: a plurality of wells extending from a top surface of thesubstrate, wherein each of the plurality of wells is configured toaccept a post enhanced diode, wherein the post enhanced diode includes apost extending from a top surface of a diode structure, wherein anorientation of a post enhanced diode where the post extends away fromthe substrate is a non-inverted orientation, and wherein an orientationof a post enhanced diode where the post extends toward the substrate isan inverted orientation; and at least one groove extending into the topsurface of the substrate and configured such that the post enhanceddiode traversing the at least one groove in the non-inverted orientationis more mechanically stable than the post enhanced diode traversing theat least one groove in the inverted orientation.
 2. The substrate ofclaim 1, wherein a depth of the groove into the substrate is less than adistance from an edge of a top surface of the diode structure to an edgeof the post.
 3. The substrate of claim 1, wherein a width of the grooveat the top surface of the substrate is less than a distance from an edgeof the top surface of the diode structure to an edge of the post.
 4. Thesubstrate of claim 1, wherein the at least one groove is a series of twoor more parallel grooves.
 5. The substrate of claim 4, wherein theseries of two or more parallel grooves are co-located in a region of thesubstrate that does not include any of the plurality of wells.
 6. Thesubstrate of claim 1, wherein the at least one groove extends in a lineacross a portion of the substrate, wherein the line has a length, awidth at the top surface of the substrate, and a depth into thesubstrate, wherein the width is less than the length, wherein the postof the post enhanced diode exhibits a first height, wherein the diodestructure of the post enhanced diode exhibits a second height, whereinan overall height of the post enhanced diode is the first height plusthe second height, and wherein the width of the at least one groove isless than the second height.
 7. The substrate of claim 6, wherein theline is selected from a group consisting of: a straight line, and acurvilinear line.
 8. The substrate of claim 1, wherein the at least onegroove extends in a line across a portion of the substrate, wherein theline has a length, a width at the top surface of the substrate, and adepth into the substrate, wherein the width is less than the length,wherein the post of the post enhanced diode exhibits a distance from anupper surface at an outer perimeter of the diode structure to an uppersurface of an outer perimeter of the post, and wherein the width of theat least one groove is less than the distance.
 9. The substrate of claim8, wherein the line is selected from a group consisting of: a straightline, and a curvilinear line.
 10. The substrate of claim 1, wherein theat least one groove extends in a line across a portion of the substrate,and wherein: the line is selected from a group consisting of: a straightline, and a curvilinear line; and wherein at least one sidewall of theline extending into the substrate is tapered.
 11. The substrate of claim10, wherein the opposing sidewall of the line extending into thesubstrate is substantially vertical.
 12. The substrate of claim 1,wherein the at least one groove is/are located together at a firstregion on the substrate and the plurality of wells are located togetherat a second region on the substrate, and wherein the first region doesnot overlap the second region.
 13. The substrate of claim 1, wherein theat least one groove is/are intermixed between the plurality of wellsacross the top surface of the substrate.
 14. A method for assembling adisplay device, the method comprising: providing a substrate, whereinthe substrate includes at least one groove extending blow a top surfaceof the substrate; providing a suspension including a carrier liquid anda plurality of post enhanced diodes, wherein each of the post enhanceddiodes includes a post extending from a top surface of a diodestructure; and orienting the plurality of post enhanced diodes inrelation to the top surface of the substrate by flowing the suspensionover the at least one groove in the top surface of the substrate,wherein an orientation of a post enhanced diode where the post extendsaway from the substrate is a more likely non-inverted orientation, andwherein an orientation of each of a post enhanced diode where the postextends toward the substrate is a less likely inverted orientation. 15.A method of claim 14, wherein the at least one groove is configured suchthat a post enhanced diode carried in the suspension across the at leastone groove in the surface of the substrate in the non-invertedorientation is more mechanically stable than the post enhanced diodecarried in the suspension across the at least one groove in the surfaceof the substrate in the inverted orientation.
 16. A method of claim 14,wherein the post is selected from a group consisting of: a non-metallicpost, and a metallic post.
 17. A method of claim 14, wherein the post isselected from a group consisting of: a non-conductive post, and aconductive post.
 18. The method of claim 14, wherein the substratefurther includes a plurality of wells extending below the top surface ofthe substrate, wherein each of the plurality of wells is configured toaccept a post enhanced diode, the method further comprising: flowing thesuspension over the top surface of the substrate such that each of theof the plurality of wells is filled with a respective one of theplurality of post enhanced diodes in the non-inverted orientation. 19.The method of claim 14, wherein the at least one groove extends in aline across a portion of the substrate, and wherein the line is selectedfrom a group consisting of: a straight line, and a curvilinear line. 20.The method of claim 19, wherein at least one sidewall of the lineextending into the substrate is tapered.
 21. The method of claim 20,wherein at least one sidewall of the line extending into the substrateis substantially vertical.
 22. A method for assembling a display device,the method comprising: providing a substrate, wherein the substrateincludes a plurality of wells extending into the top surface of thesubstrate, wherein each of the plurality of wells is configured toaccept a post enhanced diode; providing a suspension including a carrierliquid and a plurality of post enhanced diodes, wherein each of the postenhanced diodes includes a post extending from a top surface of a diodestructure; and orienting the plurality of post enhanced diodes inrelation to the top surface of the substrate by flowing the suspensionover the plurality of wells, wherein an orientation of a post enhanceddiode where the post extends away from the substrate is a non-invertedorientation, wherein an orientation of each of a post enhanced diodewhere the post extends toward the substrate is an inverted orientation,wherein one of the plurality of post enhanced diodes deposited in arespective one of the plurality of wells is more mechanically stable inthe non-inverted orientation than in the inverted orientation.
 23. Themethod of claim 22, wherein the substrate further includes at least onegroove extending into a top surface of the substrate, the method furthercomprising: flowing the suspension over the at least one groove in thetop surface of the substrate, wherein flowing past the at least onegroove makes the non-inverted orientation more likely than the invertedorientation.
 24. A method of claim 22, wherein the post is selected froma group consisting of: a non-metallic post, and a metallic post.
 25. Amethod of claim 22, wherein the post is selected from a group consistingof: a non-conductive post, and a conductive post.